The man known as the “bookkeeper of Auschwitz” who in 2015 became one of the last people to be convicted for crimes in the Nazi genocide of Europe’s Jews during World War Two, has died aged 96, magazine Der Spiegel reported on Monday.

Oskar Groening was sentenced to four years for his role as an accessory to the murder of 300,000 of the Auschwitz concentration camp’s roughly 1 million victims. He was in hospital when he died and had yet to begin his sentence.

Spiegel said Groening died on Friday but prison authorities had yet to receive a death certificate. He did not take part in any killings himself but counted cash taken from victims on their arrival at the camp.

Groening’s court battle was seen as one of the last major trials related to the Holocaust, during which some 6 million Jews were murdered by Adolf Hitler’s regime. Despite his conviction, the start of his sentence was delayed by legal wrangling and his ill health.

He came to attention in 2005 after giving interviews about his work in the camp in an attempt to persuade Holocaust deniers that the genocide had taken place at a time when most Holocaust prosecutions still focused on leaders rather than rank-and-file perpetrators.

Groening admitted he was morally guilty for the work he carried out at Auschwitz, which included sending bank notes he found in Jews’ luggage to SS offices in Berlin, where they helped to fund the Nazi war effort.